$ {4\cdot \left[ \begin{array}{cc} -1 & -2 \\ -2 & -1 \end{array} \right]=}$
The Strategy To multiply a matrix by a scalar, we multiply each term of the matrix by the scalar. Multiplying each term $ {\begin{aligned}4\cdot \left[\begin{array}{rr} {-1} & {-2} \\ {-2} & {-1} \end{array}\right]&=\left[\begin{array}{rr} 4\cdot{-1} & 4\cdot{-2} \\ 4\cdot{-2} & 4\cdot{-1} \end{array}\right] \\\\&=\left[\begin{array}{rr} {-4} & {-8} \\ {-8} & {-4} \end{array}\right]\end{aligned}}$ Summary ${4\cdot \left[ \begin{array}{cc} -1 & -2 \\ -2 & -1 \end{array} \right]=\left[ \begin{array}{cc} -4 & -8 \\ -8 & -4 \end{array} \right]}$